The invention relates to a lamp, in particular, a metal halide discharge lamp having a protective sleeve surrounding an arc tube, wherein the sleeve and the arc tube are supported by a metal frame mounted to the stem, and a glass envelope fixed to the stem surrounds the sleeve.
Metal halide lamps typically incorporate a tubular shield surrounding the pressurized arc tube to absorb the impact of dispersing shards in the event the arc tube fractures. Both the shield and the arc tube are supported by a metal frame mounted to the stem, which frame is electrically isolated from the leads for the arc tube. This is especially important for high wattage lamps. Since current carrying members in proximity to the arc tube can cause sodium loss, it is preferable to electrically distance the current carriers from the lateral walls of the arc tube.
U.S. Ser. No. 09/165,681 discloses a metal halide lamp of the type described above, wherein an arc tube and the surrounding shield are supported by a metal frame mounted to the stem. Current is supplied to the arc tube by a braided wire for the lower electrode and a flying lead well spaced from the arc tube for the upper electrode. The construction is especially suitable for a 1000 watt lamp.
Mica shields have been incorporated into metal halide lamps to reduce the amount of reflected heat to the lamp stem or base area, as well as to reduce photo-emissions of the tungsten filament in fail-safe lamps. However, the dome of the outer bulb envelope is left unprotected.
In order to increase safety, it is desirable to protect the dome of the outer bulb envelope if the lamp fails, e.g., during force rupture of the lamp, with minimal increase in manufacturing costs in a lamp having an electrically floating frame.
According to the invention, a lamp includes a light source having a pair of opposed pinched ends; and a wire frame formed from a pair of substantially parallel wire frame members and a top section where the two frame members meet. A tubular sleeve surrounds the light source between the frame members. The lamp also includes a disk having a slot where the disk is inserted over the top section through the slot. A clip is attached to the tip of the top section and holds the disk in place. The clip has bent sides that form corners which contact the disk. In the event of arc tube failure, the disk protects the dome of the glass outer envelope of the lamp, by assuring that flying fragments will not hit the dome of the outer envelope and cause it to fracture.
These and further advantages will be apparent from the drawing and description which follow.